onnxruntime

152d01f7 - Handle non-trivially-copyable types in Loop/Scan output concatenation (#29397)

Handle non-trivially-copyable types in Loop/Scan output concatenation (#29397) This pull request improves the handling of string tensors in the CPU implementation of the Loop operator, ensuring correct memory management and copy semantics for non-trivially-copyable types like `std::string`. It also adds comprehensive unit tests to verify these behaviors, especially for cases involving string scan outputs and loop-carried variables. **Enhancements for string tensor support:** * Updated `ConcatenateCpuOutput` in `loop.cc` to properly detect string tensors and use `std::copy` for concatenation, ensuring correct handling of heap-allocated string payloads and avoiding unsafe byte-wise copying. [[1]](diffhunk://#diff-2c8478657254a53c4ce09684960c925593395336e00c43ef672d9427722e3ff7R276-L282) [[2]](diffhunk://#diff-2c8478657254a53c4ce09684960c925593395336e00c43ef672d9427722e3ff7R289-R304) * Modified `OutputIterator::ZeroOutCurrent` in `scan_utils.h` to skip zeroing for string tensors, as their elements are already default-constructed and cannot be safely set with `memset`. **New and extended unit tests for string tensor scenarios:** * Added tests to `loop_test.cc` covering: - String scan outputs, including long strings that exceed the small-string-optimization threshold and multi-element outputs. - Loop-carried string variables to ensure they are copied correctly. - Zero-iteration cases to confirm empty string scan outputs are handled without errors.